A drug driving the hypothesis that a buildup of amyloid beta in the brain triggers Alzheimer’s disease failed to work in a large trial of dementia patients. Proponents of the theory note that the particular way in which solanezumab, the drug involved in the trial, works could have led to the failure, rather than a flaw in the hypothesis itself. And many trials are ongoing to test whether solanezumab — or others that target amyloid — could work in people at risk of the disease who have not yet shown symptoms, or even in people with Alzheimer’s, despite the latest negative result.

When we over-indulge on Thanksgiving we inevitably wind up feeling really lethargic and sleepy. A study conducted in fruit flies offers some insights into what might be triggering these so-called food comas. A study led by the Scripps Research Institute in Florida created a system that can measure both the sleep and feeding behaviors of individual fruit flies and discovered that, in much the same way as humans, the animals sleep for longer periods following larger meals. Further studies also revealed that certain types of food can promote post-meal sleep. The findings were published in the online journal eLife.

Those 10 million microbial genes—mostly bacterial, but also viral, fungal and parasitical—that comprise what is known collectively as the microbiome could be one reason why yo-yo dieting doesn’t lead to long-term weight loss. A study led by the Weizmann Institute of Science tracked how the intestinal microbiomes of obese mice changed as they cycled between “normal chow” and a “high-fat diet,” with their weights oscillating in sync to the shifts. The researchers identified 773 bacterial genes overrepresented when the mice ate fatty food that remained overabundant when regular chow resumed. Genes involved in the synthesis of plant compounds called flavonoids in particular became depleted after bouts of obesity.